Patent GB-650529-A (GB)
Title: Improvements in grinding wheels
IPC: B24D7/04
Filed: 1946-10-21
Abstract: 650,529. Abrasive wheels. NORTON GRINDING WHEEL CO., Ltd. Oct. 21, 1946, No. 28092/49. Convention date, Oct. 20, 1945. Divided out of 650,452. [Class 60] A face grinding wheel comprises an abrasive annulus of diamond grains distributed in a vitrified bond and a supporting annulus of granular body material distributed in a vitrified bond underlying said abrasive layer, the annuli being integrally united by a thin intermediate layer of vitrified bond. A cup wheel comprises an abrasive annulus G and a disc-like back B; the abrasive annulus G, which owing to the high cost of the abrasive is thin, is supported by an underlayer U, and the required depth of wheel is obtained by using ring elements R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP>. The abrasive annulus G comprises diamond grains bonded by a ceramic or vitrified bond; the underlayer U comprises granular body material distributed in a vitrified bond; the annulus G and underlayer U are united by a thin layer L of raw bond material; to form a composite abrasive annulus A comparable, for handling purposes, to the ring elements R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP>. The ring ele- R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP> comprise granular body material and a ceramic or vitrified bond. The composite abrasive annulus A and the ring elements R<SP>1</SP> R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP> are bonded to each other by ceramic or vitrified bonds J, J<SP>1</SP>, J<SP>2</SP>, J<SP>3</SP>. The granular body material of the ring elements may be fused alumina, 200-300 grit size, 1 per cent-15 per cent by volume; alternatively, the granular body material of the ring elements may be vitreous silica and fused alumina mixed, the abrasive annulus G containing only vitreous silica as a filler. The ceramic or vitrified bond for the abrasive annulus G, underlayer U and ring elements R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP> and for bonding these parts together may comprise ball clay and a frit, composed of borax, boric acid, silica, hydrate of alumina and whiting; alternatively, the bond may comprise Kentucky ball clay, ground flint and borax. Any suitable liquid form of binder may be used to plasticize the mix and give strength in the " green " stage. Protective agents such as aluminium, silicon (or compounds thereof) or boron (or compounds thereof) may be employed in the mix, serving also as body materials. Specification 552,246 and U.S.A. Specification 2,356,938 are referred to. The back B may be steel or other metal, cured resins, usually synthetic, such as phenolic formaldehyde resin, aniline formaldehyde resin, or other " resinoids," hardened, cured or vulcanized natural or synthetic rubber or vitrified ceramic material, or it may comprise resinoid-bonded metal particles or powder, e.g. powdered aluminium. When the back B is ceramic, the bond J<SP>4</SP> between it and the ring element R' is ceramic or vitrified bond; when the back B is non- ceramic, the bond between it and the ring element R<SP>4</SP> is a cement giving a rigid joint, e.g. synthetic resins such as phenol formaldehyde, aniline formaldehyde, applied in liquid or semi-liquid condition, and heatcurable or cold-setting. Natural or synthetic rubber, compounded and cured or vulcanized to hard condition may be used. Specification 616,019 also is referred to.